Had a look at the owners manual etc , heavy fog here this morning and I thought the auto headlights would come on then press the buttons for fog lights. The lighting dial I set to auto when first got the car ..never touched it since! Headlights didn’t turn on. I’ll remember next time it’s got to be manually turned on. (Unless anyone knows otherwise?) . 
I was checking the Service Portfolio, I’m at 13k now. Realised my Warranty Certificate is blank! Never been filled in when the dealership and I accepted the car. Has everyone else got theirs filled in? 
Mines a lease car. I’m not sure if that makes a difference...

1 hour ago, Alex.S said:

Had a look at the owners manual etc , heavy fog here this morning and I thought the auto headlights would come on then press the buttons for fog lights. The lighting dial I set to auto when first got the car ..never touched it since! Headlights didn’t turn on. I’ll remember next time it’s got to be manually turned on. (Unless anyone knows otherwise?) . 
I was checking the Service Portfolio, I’m at 13k now. Realised my Warranty Certificate is blank! Never been filled in when the dealership and I accepted the car. Has everyone else got theirs filled in?

Found similar with my Fiesta. Like the autowipers it's a bit hit and miss and I sometimes find them not coming on when I would have expected (including fog). Conversely they sometimes switch on when lighting conditions are good. I disabled the wipers so they operate as normal intermittent, I'd swap the autolights for a manual switch if I could.

My warranty certificate wasn't filled in either, nor was my Mrs's which is a different make. Not sure I can remember ever seeing one filled in, tbh.

 

Auto lights just react to light and dark, they have no idea that its foggy, you need to switch them on manually in the fog. All auto light switches also have manual settings for Off/Parking Lights/Headlights.

Later cars have 'rain lights' as an option in the dash which automatically switches the lights on when the wipers are on.  Can be useful if the fog is thick enough to trigger the wipers.

Focus 4 with autolights has that as standard ie lights come on if wipers operate for a while. However re fog problem is that although visibility may be significantly impaired light level is often  too high for lights to come on, hence the need to switch them on manually. It does indicate that in owners handbook.

Also the MK4 Focus lights go to auto, automatically. In the MK3, it never did that. 

That's an EU lighting regulation. All new cars will be the same. Again its in the handbook.